This study is directed to the purification, characterization and investigation of an extracellular ribonuclease (barnase) of B. amyloliquefaciens and its natural inhibitor, (barstar, from the same source) and to the development of methods of culture and genetic analysis so that the organism and its product pair may be applied to a long-range study of enzyme structure, function and synthesis. Specific objectives are: (1) the determination of the amino-acid sequence and three-dimensional structure (by X-ray diffraction) of both proteins and the structure of their complexes; (2) thermodynamic and kinetic analysis of structural transitions produced in both proteins by heat or denaturing reagents; (3) analysis of the folding and activity of both by means of peptide complementation systems analogous to those being used for the study of pancreatic ribonuclease and micrococcal nuclease; (4) all of the above with chemically and/or genetically modified sequences.